The invention relates to a hip-joint socket of a hip-joint endoprosthesis in accordance with the preamble of the first claim.
Hip-joint endoprostheses as a rule are build up in a modular fashion. They consist, for example, of a shaft which is inserted into the femur. Plugged onto the shaft is a ball head which is mounted in a socket that is constructed from two parts. The socket consists of a socket housing, the so-called metal back, and a socket insert, the so-called insert. Furthermore, there are also systems which permit even more possibilities of combination and variation, for example in order to lengthen the shaft. With the modularly built up endoprostheses, implant components of different materials and sizes are connected together. For example, ball heads made of cobalt chromium are plugged onto a shaft of titanium alloy, or a socket insert of polyethylene or a ceramic material is inserted into a socket housing, as known, for example, from DE 196 112 48 A1. The combination of the individual parts is, as a rule, predetermined by the dimensions of the joint.
As known from the publication "Frettingkorrosion, ein Problem bei Huftendoprothesen" by G. Willmann, Praktische Orthopadie, Rheumatologie-Endoprothetik, Volume 27, 1997, the disadvantage of the modular construction of endoprostheses is that, after having been assembled, instances of loosening can occur as a result of strains in the body that result in the relative movement between the individual parts of the prostheses and thus give rise to wear. In addition, on account of the plurality of possible components and possibilities for the assembly thereof, there is also a risk of confusion with regard to the sizes or a combination of prosthesis components that is not as prescribed. This can result in defective functioning of the prosthesis and thus ultimately in failure.